This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-287658, filed Sep. 20, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a module for optical communications, for example, which coverts a light signal to signals of a differential form and outputs the signals, or which emits the light signal in response to the inputted differential signals.
2. Description of the Related Art
In recent years, due to the explosive growth of communication demands brought about by the Internet, there are now strong demands for an optical communications system. In an optical communications system, a module for an optical communications for use in a light transmitter/receiver has been required to be reduced in size and cost.
FIG. 10A schematically shows a first example of a conventional module for the optical communications. As shown in FIG. 10A, a module for optical communications 101 includes a package 102 in which a light receiving element and wiring substrate described later are contained. In the package 102, there are disposed: a light receiving element 104 which receives a light incident from an optical fiber 103 and photoelectrically converts the light; and a wiring substrate 105. On the wiring substrate 105, there are disposed: semiconductor devices (hereinafter referred to as IC) such as a preamplifier 106 which amplifies a signal from the light receiving element 104; and wiring patterns 107a, 107b. 
For an output of the preamplifier 106, in recent years, a differential output form has frequently been used which has a reverse and non-reverse outputs in order to enhance an SN ratio with respect to an external noise. In this conventional example, for example, a connection pad 108a formed on an upper side outputs the non-reverse output, and a connection pad 108b on a lower side outputs the reverse output. The wiring patterns 107a, 107b substantially have symmetric shapes in a perpendicular direction, and these wiring patterns 107a, 107b are disposed opposite to each other. The connection pads 108a, 108b and wiring patterns 107a, 107b are connected to each other via bonding wires 109. The wiring patterns 107a, 107b are connected to lead pins 110a, 110b in ends of the wiring substrate 105.
The above-described module for optical communications 101 is disposed, for example, on a substrate, and the substrate is assembled in various apparatuses for use.
FIG. 11 shows a second conventional example of the module for optical communications. As shown in FIG. 11, a module for optical communications 121 includes the light receiving element 104 and wiring substrate 105 in the package 102.
An IC 122 is disposed on the wiring substrate 105. The IC 122 includes a connection pin 123a which outputs the reverse output and a connection pin 123b which outputs the non-reverse output. The connection pins 123a, 123b are connected to wiring patterns 124a, 124b. The wiring patterns 124a, 124b are respectively connected to the lead pins 110a, 110b, for example, via bonding wires.
Additionally, in the first conventional example, the lead pin 110a is connected to the connection pad 108a to output the non-reverse output, and the lead pin 10b is connected to the connection pad 108b to output the reverse output. However, in general, the arrangement of these lead pins is not optionally determined. In some apparatus (substrate) in which the module for optical communications 101 is assembled, a side on which the connection pads 108a, 108b of the IC 106 are formed does not meet with a side on which the lead pins 110a, 110b are formed. That is, the lead pin 110a forms the reverse output, and the lead pin 110b forms the non-reverse output. In this case, a separate IC needs to be prepared in which the upper connection pad 108a forms the reverse output, and the lower connection pad 108b forms the non-reverse output. This increases costs. Moreover, the IC with a connection pad arrangement that meets the demand of a user may not be manufactured.
Furthermore, conversely, depending on an IC maker, different from the aforementioned IC 106, the positions of the reverse output and non-reverse output may be reversed. Therefore, similarly, connection relations between the connection pads 108a, 108b and lead pins 110a, 10b need to be reversed.
To switch the reverse and non-reverse outputs of the module for optical communications 101 without changing the arrangement of the wiring patterns 107a, 107b, for example, as shown in FIG. 10B, a method is considered comprising: allowing the bonding wires 109 for connecting the connection pads 108a, 108b to the wiring patterns 107a, 107b to intersect with each other. That is, the connection pad 108a is connected to the wiring pattern 107b, and the connection pad 108b is connected to the wiring pattern 107a. 
In this method, however, since the bonding wires 109 intersect, there is a possibility of short-circuit. Moreover, since the bonding wires 109 are disposed in the vicinity of each other, a problem is deterioration of frequency properties by mutual inductance between the bonding wires 109.
Moreover, in the second conventional example, for similar reasons, the connection pins 123a, 123b of the IC 122 may not be on the same side as the lead pins 110a, 110b in some cases. In this case, similarly as the first conventional art, it is necessary to prepare a separate IC that satisfies the condition, or a new wiring substrate 105 including the wiring pattern which satisfies the condition. This not only complicates a manufacturing process of the module for optical communications but also increases costs.
According to a first aspect of the present invention, there is provided a module for optical communications comprising: a light receiving element receiving the light signal and converting the light signal to an electric signal; an insulating substrate including a first major surface and a second major surface opposite to the first major surface; an output section provided on the first major surface and extracting the electric signal as a reverse signal and non-reverse signal; first and second connection terminals connected to the output section, the reverse signal being outputted via the first connection terminal, the non-reverse signal being outputted via the second connection terminal; and first and second wiring patterns provided on the first major surface, one of the first and second wiring patterns being electrically connected to the first connection terminal, the other one of the first and second wiring patterns being electrically connected to the second connection terminal, the first wiring pattern including a first end, the second wiring pattern including a second end, and the first and second ends being provided in order in a direction intersecting with a line connecting the first and second connection terminals.